The present invention relates to a multifunction key for use with a portable device, such as a mobile telephone, a portable CD or MD player, or a portable game machine, which prevents simultaneous pressing of keys, to thereby improve operability.
In order to improve the operability of a portable device, such as a portable telephone, a cordless telephone, a portable CD or MD player, or portable game, or a like, a single key is employed so as to enable the user to issue a plurality of operation instructions by actuation of a single key. Such a single key is called a multifunction key, and examples of a conventional multifunction key are shown in FIGS. 17 and 18.
A multifunction key "a" shown in FIG. 17 enables entry of six different operation instructions; i.e., an up instruction, a down instruction, a left instruction, a right instruction, a call instruction, and a function (F) instruction, by actuation of a single multifunction key.
The call instruction and the function (F) instruction are performed by pressing the multifunction key "a" for a relatively longer period of time.
A multifunction key "b" shown in FIG. 18 is arranged so as to be enable the user to input four different operation instructions; i.e., an up instruction, a down instruction, a left instruction, and a right instruction, by actuation of a single multifunction key.
Each of the multifunction keys "a" and "b" shown in FIGS. 17 and 18 enables entry of a plurality of different operation instructions. A plurality of operation instructions can be issued by actuation of only a single multifunction key, thus improving operability of a portable device.
However, the multifunction keys "a" and "b" shown in FIGS. 17 and 18 suffer the following problems.
In order to execute the operation instruction entered by means of the multifunction key "a" or "b"; for example, a call origination instruction or a re-dialing instruction, another key spaced apart from the multifunction key "a" or "b" must be actuated by use of a finger. Thus, a key other than the multifunction key "a" or "b" must be actuated every time an operation instruction is to be issued, thus deteriorating the operability of the portable device.
In association with a reduction in the size and weight of the portable devices, the multifunction keys "a" and "b" themselves have become smaller. When the small-sized multifunction key "a" or "b" is actuated so as to select one from the operation instructions assigned to the multifunction key, an undesired operation instruction may also be selected and actuated in addition to a predetermined operation instruction by two-stage pressing action.